1. Field of the Invention
The present invention relates to an application sharing system for exchanging and sharing information among a plurality of terminal apparatuses in a conferencing system utilizing information processing apparatuses including a computer and communication equipment.
2. Description of the Related Art
Application sharing systems according to the prior art include systems which enable a plurality of terminals to share the result and process of the execution of an application program by multicast delivery of information not dependent on any application program to the same application program in response to an input from any terminal, disclosed in the Japanese Patent Application Laid-open No. Hei-6-83785 or a paper by ABE et al. entitled "Distributed Cooperative Control for Sharing Applications Based on the MERMAID Multiparty and Multimedia Desktop Conferencing System" published in NEC Corporation, NEC RESEARCH & DEVELOPMENT, Vol. 34, No., pp. 122-131, January 1993.
The term "application sharing" means the sharing of the result of processing of multicast operation of a single application by a plurality of users from their respective terminals, and the term "application program", collaborating application programs operating on different terminals as if they were a single application program and realizing application sharing by carrying out processing while exchanging information among one another.
FIG. 11 is a block diagram illustrating the overall configuration of the system, out of the techniques according to the prior art referred to above, disclosed in the Japanese Patent Application Laid-open No. Hei-6-83785. Referring to FIG. 11, this system is provided with a plurality of terminal systems 11, 12 and 13 and a terminal system 10 including one multicast communication control means 120. Since the terminal systems 11, 12 and 13 have the same configuration, only the terminal system 11 will be described below as representative of the plurality of systems.
The terminal system 11 has execution control means for an application program 531 consisting of event providing means 541, event analyzing means 551, message communicating means 571 and procedure executing means 561. The event providing means 541 enters event information into the event analyzing means 551, which analyzes the entered event, prepares a message for requesting the execution of a processing procedure for the application program, adds to or includes in the message information required for sharing action, and enters the message into the message communicating means 571, which in turn transmits the message to the multicast communication control means 120 via a line 21.
The multicast communication control means 120, utilizing the information added to or included in the received message, transmits this message to message communicating means of the plurality of terminal systems 12 and 13; the message communicating means 572 and 573 in the terminal systems 12 and 13 extract from the messages received from the multicast control means 120 via lines 22 and 23, respectively, the information (necessary information for sharing action) added to or included in the messages, enter the information into procedure executing means 562 and 563 of the application programs 532 and 533, respectively; and the procedure executing means 562 and 563 perform processing using the respectively entered messages; and the application programs on the plurality of terminal systems 11, 12 and 13 process event information generated on the respective terminal systems, and obtain the same result of execution. In this manner, an application program is shared by the plurality of terminal systems 11, 12 and 13 on a real time basis.
However, the above-described system according to the prior art involves the problem that, where the same information is subjected to multicast delivery from one application to a plurality of other applications, the multicast communication control means is used and, since the multicast communication control means use consecutive multicast communication, i.e. information being individually delivered to each application, the cost of multicast communication per item of information increases in proportion to the number of terminals.
The prior art system described above also involves the problem of complexity of processing at the time of starting or ending the system because the multicast communication control means is independent of other programs and operates by itself.
Furthermore, the conventional system described above involves the problem that the terminals can participate in only a specific conferencing system on account of the lack of means to permit participation in any desired one out of a plurality of conferencing systems.
It also has the problem of requiring another terminal (for instance the terminal 10 provided with the multicast communication control means 120 in FIG. 11) separately from the terminals of users participating in the conference.
Moreover, the prior art system involves the problem that application sharing is impossible among terminals not connected to the same communication network because it presupposes the connection of any terminal to the same communication network as other terminals.
Therefore, the object of the present invention, attempted in view of the above-described circumstances, is to provide an application sharing system which makes it possible to use a communication path at a favorable transfer efficiency by differentiated use of multicast communication and unicast communication, to compose a conferencing system of user terminals alone by providing each terminal with a function to manage a conferencing group and, where there are a plurality of communication paths, to choose the optimal path.